1. Field
The present disclosure relates to an electrophotographic toner and a process of preparing the same.
2. Description of the Related Art
In electrophotographic processes or electrostatic recording processes, developers for developing electrostatic images or electrostatic latent images are classified into two-component developers formed of a toner and carrier particles, and one-component developers substantially formed of only a toner, that is, developers that are not formed of carrier particles. The one-component developers may be classified into magnetic one-component developers containing a magnetic component, and nonmagnetic one-component developers not containing a magnetic component. Plasticizers such as colloidal silica may be often independently added to nonmagnetic one-component developers to improve toner fluidity. In general, coloring particles obtained by dispersing a coloring agent, such as carbon black, or other additives in a latex are used as a toner.
Toners may be prepared using a pulverization method or a polymerizing method. In the pulverization method, a synthesized resin, a coloring agent, and when required, other additives are melted, pulverized, and then sorted to obtain particles having desired diameters, to thereby obtain a toner. In the polymerizing method, a coloring agent, a polymerization initiator, and when required, other additives, such as a crosslinking agent or an antistatic agent, are uniformly dissolved in or dispersed into a polymerizable monomer to prepare a polymerizable monomer composition. Then, the polymerizable monomer composition is dispersed into an aqueous dispersion medium including a dispersion stabilizer, using a stirrer to form micro droplet particles of the polymerizable monomer composition. Subsequently, a temperature of the mixture of the medium and the micro droplet particles is increased and then a suspension polymerization process is performed to obtain colored polymerization particles having desired diameters, to thereby obtain a polymerized toner.
Toners used for image forming apparatuses are mainly prepared through a pulverization method. In the pulverization method, since a toner particle size, a geometric size distribution, and a toner structure are not accurately controlled, it is difficult to independently adjust important characteristics required for a toner, such as charging, fixation, fluidity, and storability.
A polymerized toner having an easily obtained particle diameter does not require a complex manufacturing process, such as classification, has recently received a great amount of attention. By using such a polymerization method, a toner having a desired particle diameter and a desired particle diameter distribution may be prepared without pulverization and classification. In order to uniformly control geometric sizes or shapes during a polymerization process, a coagulating method has been suggested as a toner preparing process that uses a metallic salt, such as MgCl2 and NaCl, or a polymer such as poly aluminium chloride (PAC).
If a metallic salt coagulant is used, geometric sizes and particle distribution of a toner can be controlled and capsule structures having shells can be constructed to some degree of reproducibility, and thus a metallic salt coagulant may be put to practical use in toner formation. However, there are limitations in uniform control of geometric sizes and shapes. That is, although the granularity of a toner can be well controlled in a central toner particle size range, the shape of toner particles tends to be undesirably spherical in a small toner particle range. This may cause an issue in regard to blade cleaning during electrophotographic processes.
Additionally, a toner having both a high gloss and a wide fixation region can be prepared by controlling a coagulating process during formation of the toner so that the toner have a capsule structure. In the case of a toner having a capsule structure, since a pigment and a release agent are not exposed, charging uniformity, fluidity, and heat storability may be ensured to some degree. An anti-offset characteristic of a toner is important for ensuring stable fixation of the toner and is closely related to rheological properties of the toner. Properties of a toner such as molecular weight and crosslinking, or use of a release agent are considered to control the anti-off characteristic of the toner.